This invention relates to an induction heating apparatus and more particularly to an apparatus which is designed to heat, conductive, adhesive-backed fasteners.
Induction heating techniques for the securement of heat activable adhesive are known generally in the prior art. More particularly, the use of a U-shaped core in association with an article to be heated has been found to be an effective and efficient manner of generating heat in an adhesive-backed conductive article. In such a system, the upper surface of the conductive article is positioned to bridge the legs of the core so that a magnetic flux circuit is completed between the core and the article. Since the core will typically be of a low loss material and the article will be of a high loss material, heat is effectively generated by eddy currents in the article and hysteresis effect. The heat generated in the article thus serves as the source to activate the adhesive coating.
Although one of the major advantages of such a system is the efficiency in which heat can be generated and utilized, it becomes important that the article to be heated is accurately and carefully positioned relative to the end faces of the core so that the heating pattern is uniform and so there is a minimum of flux loss in the system since the flux density in the article is directly related to the amount of heat generated therein.
A proper adhesive bond also requires carefully controlled pressure to be exerted on the article during the heating and flowing of the adhesive so that the faying surfaces are subjected to the maximum wetting.
High-production rate applications of adhesive-backed articles, including applications requiring a plurality of articles to be assembled substantially simultaneously on a predetermined area of a support surface, are particularly sensitive to the situations noted above and therefore there is a need for a properly designed fixture for uniformly and accurately applying heat and pressure to an adhesive-backed article which will accommodate various support surfaces and/or curvatures thereof.